According to Wookieepedia, the Death Star 1's diameter is 160 km, while Alderaan's is 12,000 km. After shooting Alderaan one can assume there should be large and very fast chunks of the planet flying towards the Death Star. To put these dimensions in context, a small asteroid over 100 m caused the Tunguska event devastating 2000 square kilometres. How did the Space Station manage this? Can its shields deflect large asteroids?

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    12000km diameter planet = 1.1e6 square km of debris. Death Star max range is 2000000km to 240000000km. Effective volume is 2.5e13 to 1.8e17 so around 2 parts per 1e7 to 1e11. Very good chance of avoiding everything, if anything got close they have plenty of time to respond. Minimum distance is 6 light seconds, suppose the matter flies away at 6x the speed of sound they have 11 days to respond. Commented Jun 16, 2013 at 15:59
  • @GorchestopherH - you should make this an answer.
    – user8719
    Commented Jun 16, 2013 at 16:58
  • Also, they had tractor beams... ;)
    – C.B.
    Commented Jun 16, 2013 at 19:07

5 Answers 5


These calculations are approximate:

12000km diameter planet = 1.1e6 square km of debris.
Death Star max range is 2000000km to 240000000km.
Effective volume is 2.5e13 to 1.8e17 so around 2 parts per 1e7 to 1e11.

Given the above, there is a good chance of avoiding everything, if anything got close they have plenty of time to respond. Recommended operational distance is 6 light seconds, suppose that matter flies away at 6x the speed of sound they have 11 days to respond to incoming debris.

This is a simple matter for a fleet of Tie fighters and a fully operational Death Star.

Information from Wookieepedia. https://starwars.fandom.com/wiki/Superlaser

  • 1
    This is a very interesting answer, however I'm slightly concerned with the range figures being used. (1) The range on Wookiepedia doesn't have a canon reference for the range; (2) There's no canon indication that Death Star was at the end of the range as opposed to closer in. Commented Jun 16, 2013 at 19:29
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    Even if the Death Star was really really really close in, it's difficult to imagine it having any kind of time period less than hours in which to respond to incoming threat. This isn't canon, it's basic physics.
    – user8719
    Commented Jun 16, 2013 at 20:04
  • 1
    The speed estimate should be much higher. Assume planetary escape velocity minimum, several miles per second, else you get no explosion. Six light seconds away is a comfortable margin of safety, but in Star Wars the Death Star looked much closer.
    – Kyle Jones
    Commented Jun 16, 2013 at 20:20
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    We can actually work out the distance based on relative sizes from e.g the famous shot here: theforce.net/swtc/Pix/given/fg/alderaan2.jpg - if I have the calculations right it's about 8.5 million km, or 28 light seconds. At an extremely generous 25 km/s for debris, it would have taken 4 days to reach the Death Star's location when it blew it up - nothing to worry about. youtube.com/watch?v=djZFHTa6TfA establishes an absolute minimum distance of ~2 light seconds, which still gives the DS over 6 hours to get away (assuming 25km/s). Still not a problem.
    – user8719
    Commented Jun 16, 2013 at 21:31
  • Since the Death Star is completely capable of firing from a "safe" range, I imagine it would have. Commented Jun 17, 2013 at 4:04

According to C-canon ("Death Star" book by by Michael Reaves and Steve Perry), most of the mass of the targeted planed is NOT exploded outward as matter:

It took no more than an instant. Tenn knew that the beam's total destructive power was much bigger than matter-energy conversions limited to realspace. At full charge, the hyper-matter reactor provided a superluminal "boost" that caused much of the planet's mass to be shifted immediately into hyperspace. As a result, Alderaan exploded into a fiery ball of eye-smiting light almost instantaneously, and a planar ring of energy reflux-the "shadow" of a hyperspatial ripple-spread rapidly outward.

In other words,

  1. There was no mass of debris for Death Star to worry about avoiding. Instead of a mass of planets, what was left was light and some chunks (as can be seen in the movie) that look like a lot but - at a significant distance - constitute much less of a threat of a hit.

  2. Most of the explosive energy was converted into hyperspace and into light - less was left to impart enough kinetic energy to those chunks to accelerate far.

  • 3
    The asteroid field it left behind (described as extremely dense in many EU books and seen in the movies) indicates that it DID, indeed, leave a significant debris field. Sure, Death Star contradicts this point, but when books contradict the movies, the movies win.
    – Jeff
    Commented Jun 16, 2013 at 16:39
  • 1
    @Jeff - there's a difference between "have to dodge enough material to have constituted a planet" vs "have to dodge enough material to leave an asteroid field". FYI, asteroid fields are VERY sparse, even ones that are considered "dense" by navigational standards. Commented Jun 16, 2013 at 17:51
  • 1
    Isn't it possible some of the mass leapt out of subspace after a bit? Conveniently without significant momentum. That would explain how Alderaan could vanish in one moment, leaving only tiny bits behind (as shown in the film) but allow for the asteroid field the Falcon flies in later on.
    – bitmask
    Commented Jun 16, 2013 at 19:08
  • 2
    @bitmask - I think you meant 1 parsec of Fail points Commented Jun 16, 2013 at 20:30
  • 3
    @DVK - no, everybody knows that parsec is a time measurement. ;)
    – user8719
    Commented Jun 17, 2013 at 0:45

In the Star Wars Universe, what shields can block is determined by how many shield projectors you have and how much power you give them. The Death Star is described as having many, many projectors and a LOT of power to work with. It may very well be able to deflect a large chunk of planet.

It wouldn't need to, however.

As you can see in Empire Strikes Back, Star Destroyers are more than capable of destroying even large asteroids with their turbolasers. Star Destroyers aren't in any danger of damage from a typical Star Wars asteroid field, unless your commanding officer has ordered you to drop shields so you can carry on a full-holo communication, of course.

In any case, the strength of the Death Star's shields isn't really at question - it was covered with thousands of turbolasers. This Wookieepedia article lists the first Death Star as having over 10,000 turbolasers and 2,500 laser canons. It also gives the effective range of the superweapon as 47,060,000 kilometers. Between all the turbolasers ready to superheat any incoming rocks into rapidly-dispersing plasma, extreme range meaning they have very few incoming rocks to melt, and shields that could hold off a fleet of star destroyers pretty much indefinitely, the Death Star has very little chance of immolating itself upon it's victims' funeral pyres.


Regarding the Death Star hyperspace boost

Canon novel of A NEW HOPE

"Luke had seen the shattered remains of Alderaan and knew that for those in the incredible battle station the entire moon would present simply another abstract problem in mass-energy conversion."

This over-rules the non-canon Death Star novel which mentions hyperspace mumbo-jumbo technobabble, and tells us the Death Star does indeed use a conventional hypermatter fuel consuming superlaser.

Even in the Expanded Universe the Death Star novel is an outlier as numerous other novels all simply state the Death Stars reactor builds up the energies needed for a planet destroying burst with no mention of this hyperspace stuff, and some such as "BEHIND THE MAGIC" even state the superlaser is a form of up scaled turbolaser weaponry.

Many like to read Death Stars technobbable explanation and conclude the Death Star must be less powerful to achieve this. But even if we went with the wobbly explanation in that book it would only serve to increase the firepower, not lower it, because accelerating something into FASTER THAN LIGHT SPEEDS is obviously more energy consuming than accelerating the planet to SUBLIGHT SPEEDS. Furthermore the Return of the Jedi novel even states accelerating to lightspeed is a prerequisite to jumping to FTL.


The smallest visible debris are over 100 kilometers in diameter and were travelling at thousands of kilometers per second. Debris of this size and speed would be impacting the Death Star with planet shattering energies within seconds of Alderaan being destroyed.

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